1. Field of the Invention
The present invention relates, in general, to a transmission type screen, and, more particularly, to a transmission screen for displaying stereoscopic images and which has a transmission layer for transmitting images while maintaining the degree of polarization thereof. The screen also is suitable for both stereoscopic images and general images with improved definition of the images.
2. Description for the Related Art
A transmission screen is a screen on which images are projected from the rear side of the screen and which allows a user to view images displayed on the front side of the screen.
Conventional transmission screens having transmission layers are transmission screens through which general images are transmitted, and include a medium having a refractive index, diffusion material within the medium, and diffusion material on the surface of the medium, so that in the course of transmitting polarized images, the images are not only diffused, but also the degree of polarization of the polarized images is diffused, and thus the implementation of stereoscopic images is impossible.
Some screens having a film structure, such as a film having no transmission layer, enabling transmittal of stereoscopic images, but such film screens generally have a thin-film structure and the flatness thereof is maintained only by adding separate frames and providing tension through a spring. However, there are disadvantages to such scenes in that deformation of the screen occurs due to climatic changes as time elapses and, more particularly, since the image displayed on a surface of the screen is diffused, the efficiency of transmission is less than 20%, the angle of polarization is diffused, and therefore the viewing angle becomes narrow, thereby making three-dimensional viewing uncomfortable.
For the above-described reasons, a screen having a thin film is not suitable for large screen structures or three-dimensional TV's because of limitations in frames and tension structures.
The present invention relates to a transmission screen configuration having a transmission layer greater than 1 mm, and which is suitable for use as a three-dimensional TV or a large screen.
As illustrated in FIGS. 1, 2(a) and 2(b), known stereoscopic images may be generated such that the images of left and right projectors P1 and P2 pass through left and right polarization filters R1 and L1, respectively, having polarization degrees of a symmetric angle, and wherein the left images R are transmitted only through the left polarization lens 5R of polarization glasses 5 and blocked through the right polarization lens 5L, and, in the same way, the right images L are transmitted only through the right polarization lens 5L of the polarization glasses and blocked through the left polarization lens 5R, thereby allowing the right images L to be viewed only by the right eye of a viewer and the left images R to be viewed only by the left eye of the viewer.
It is thus impossible to view the stereoscopic images without maintaining the polarization degrees of the left and right images as described above.
For use as conventional transmission screens, there are a variety of transmission screens, such as Fresnel type screens, diffusion material addition type screens, and scattering type screens, but it is impossible for a viewer to view stereoscopic images using such screens because the polarization degree of the images is diffused by the refractive index, the transmissivity, and the scattering rate when images are transmitted using such screens.
In particular, in a conventional transmission screen onto which diffusion material, such as silica, is added in order to diffuse images for screen functions, when images are transmitted, the polarization degree is also diffused, so that the polarization degrees of the left and right images R and L are reduced, and therefore, a double focused image is observed by a viewer, making viewing of stereoscopic images impossible.